In various systems, the efficiency of a system may be dependent on effectively providing cooling or sealing fluid to the system. For instance, in gas turbine systems, it may be desirable to provide cooling and/or sealing air by diverting a portion of the air in the compressor using an ejector. For instance, a first airflow may be extracted from a thirteenth stage of the compressor to cool one stage of the turbine. A second airflow may also be extracted from a ninth stage of the compressor (i.e., at a lower pressure and temperature) to another stage of the turbine. The ejector may be used to mix the first and second airflows to provide a third airflow at a temperature and pressure for cooling the appropriate turbine stage without the need to throttle (i.e., waste) airflow that may be at too high a pressure.
Typically, an ejector may be optimized for the International Organization for Standardization (ISO) conditions (i.e., 59° F. environment temperature). However, efficiency may be affected at operating conditions other than ISO conditions. In addition, typical fixed ejector designs may be operated at less than maximum efficiency under operating conditions such as the ambient environment of a location. For example, on hot days, the ejector may deliver more air than required and may overflow, while on cold days, the ejector may not deliver enough air. Thus, some ejectors designed for hotter operating conditions may not provide the required performance in colder operating conditions and vice versa. Design and use of specific ejectors for different ambient operating conditions generally may be costly, cost prohibitive, and/or labor intensive. For instance, changing the dimensions of a motive nozzle in an ejector for different operating conditions may involve changing the nozzle and the whole motive flow system, including numerous pipes and flanges, to which the motive nozzle may be welded.
Accordingly, there is a need for improved ejector which avoid one or more of the aforementioned disadvantages and deficiencies to provide improved efficiency in the systems associated with the ejectors.